This invention relates to power transmissions and more particularly to multi speed power transmissions having three simple planetary gear sets.
It has been proposed, in U.S. Pat. No. 5,599,251 to provide six forward speed ratios and a reverse ratio using three simple planetary gear sets and six friction devices. This patent describes a planetary gear arrangement that has rotating friction devices positioned between the first and second gear sets. The arrangement also requires that two of the stationary friction devices are positioned to control hub members that are also axially disposed between the first and second planetary gear sets. The positioning of these components requires a significant amount of axial space within the transmission housing which results in the overall length of the transmission being quite large.
It is an object of the present invention to provide an improved compact multi speed power transmission having three simple planetary gear sets.
In one aspect of the invention, the three simple planetary gear sets are controlled by a plurality of selectively engageable friction devices to provide six forward speed ratios, a reverse ratio, and a neutral condition. In another aspect of the present invention, the transmission employs six friction devices that are located radially outboard of the three simple planetary gear sets.
In yet another aspect of the present invention, two of the friction devices are of the rotating type (clutches) and the remaining four friction devices are of the stationary type (brakes). In still another aspect of the present invention, the three planetary gear sets are interconnected in a manner that permits one of the rotating type torque transmitting mechanisms to be positioned radially outboard of the center of the three planetary gear sets.